The present invention relates to a structure of a turning portion of an industrial robot using an eccentrically oscillating speed reducer.
There is known a structure of a turning portion of an industrial robot of a background art described in, for example, JP-A-7-124883 shown below.
According to the structure, the structure includes a first member constituting a base of the industrial robot and a second member constituting a turning portion, and an eccentrically oscillating speed reducer arranged between the first member and the second member having 2 pieces or more of crank pins and transmitting rotation provided to the crank pin to the second member by reducing a speed thereof and rotating the second member by a speed lower than that of the first member, an input gear respectively fixed to input side end portions of all of the crank pins, a rotating cylindrical member coaxial with a center axis of the eccentrically oscillating speed reducer, penetrating inside of the eccentrically oscillating speed reducer, provided with a first outer gear brought in mesh with all of the input gears at one end thereof and provided with a second outer gear at other end thereof, and an idle gear rotatably supported by the second member by way of a pair of bearings and brought in mesh with the second outer gear, and a drive motor provided with an output gear brought in mesh with an idle gear at an output shaft thereof and arranged remotely from the center axis of the eccentrically oscillating speed reducer by a predetermined distance in a radius direction.
Further, according thereto, rotation from the drive motor is transmitted to the single rotating cylindrical member by way of the output gear, the idle gear, the second outer gear, thereafter, a rotational torque is transmitted to all of the crank pins by way of the first outer gear of the rotating cylindrical member, the input gear while distributing the rotational torque substantially equally thereto.
However, according to the structure of the turning portion of an industrial robot of the background art, in order to rotatably supporting the idle gear by the second member, it is necessary to support the idle gear by the pair of bearings and integrating the pair of bearings to the second member, further, in order to avoid an interference of the input gear and the idle gear, it is necessary to penetrate the rotating cylindrical member provided with the first outer gear brought in mesh with the input gear at one end thereof and the second outer gear brought in mesh with the idle gear at other end thereof at inside of the eccentrically oscillating speed reducer, as a result, there poses a problem that an integrating operation becomes troublesome, the rotating cylindrical member is large-sized (an axial direction length thereof is prolonged) to make fabricating cost expensive.